1. Field of the Invention
The present invention relates to an aromatic o-hydroxyamide compound having an excellent ultraviolet ray absorption and heat resistance, and a polymeric composition containing the same and having an excellent ultraviolet ray resistance and mechanical strength.
2. Description of Related Art
It is known that conventional ultraviolet ray-absorbing benzophenone and benzotriazole compounds usually exhibit an ultraviolet ray-absorbing activity inherent to specific wavelengths of ultraviolet rays at a relatively low temperature. These conventional ultraviolet ray-absorbing compounds; however, exhibit an unsatisfactory thermal resistance, and thus are disadvantageous in that when the compounds are mixed into a polymeric material at a high temperature or the resultant mixture is shaped at a high temperature, most all of the compounds are thermally decomposed or sublimated.
As a measure to counter the above-mentioned disadvantage, it has been attempted to add an inorganic material, for example, fine particulate titanium dioxide, carbon black or red oxide to the polymeric material. However, this attempt is disadvantageous in that since the inorganic materials and the polymeric material are insoluble in each other, the addition of the inorganic materials usually causes the mixed polymeric material to have a reduced mechanical performance and to be colored, and thus the mixed polymeric material cannot keep a color inherent to the polymeric material per se.
Usually, polyesters, including wholly aromatic polyesters, aliphatic polyamides, wholly aromatic polyamides (aramids) and polycarbonates are mixed with an ultraviolet ray absorber during polymerization procedures, before or after shaping or molding procedures, or during post processing procedures thereof, at a high temperature to enhance their weathering resistance.
Since the conventional ultraviolet ray absorbers are unsatisfactory in thermal resistance, as mentioned above, a new type of organic ultraviolet ray absorbers having an enhanced ultraviolet ray-absorbing activity, thermal resistance and weathering resistance is in demand.
Especially, aramids have a high tensile strength, modulus and thermal resistance and thus are widely employed to produce fibers and films. However, it is well-known that aramids exhibit an unsatisfactory light resistance.
To enhance the light resistance of aramids, it has been attempted to mix an ultraviolet ray-absorbing benzotriazole compound and an anti-oxidant to a dope solution of poly-methaphenylene isophthalamide in N-methyl-2-pyrrolidone, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 49-100,322. However, the light resistance of the resultant mixed polyamide is not always satisfactory.
Also, it is known that poly-para-phenylene terephthalamide (PPTA), which is a typical para-type aramid, is difficult to melt and to dissolve in common solvents. Therefore, to produce a shaped article, it is necessary to dissolve the p-aramid in a special solvent such as sulfuric acid and then the solution is subjected to a shaping process.
Although the usual meltable or soluble polymers can be mixed with various types of additives, which impact a specific performance to the polymers without difficulty, in the case of p-aramid, the additives capable of being mixed into the p-aramid solution in the sulfuric acid solvent are strictly restricted in view of the chemical stability of the additives to sulfuric acid. As an additive usable for the p-aramid solution, carbon black is known from Japanese Unexamined Patent Publication (Kokai) No. 64-85,316 and organic solvents are known from Japanese Unexamined Patent Publication (Kokai) No. 64-14,317.
However, the use of these materials causes the resultant aramid article to be colored in a specific color, and thus cannot be used to produce an aramid article having a color inherent to the aramid per se. Also, since the additives are difficult to evenly disperse in the p-aramid solution, the resultant p-aramid article exhibits an unsatisfactory mechanical strength.
Generally, where a conventional ultraviolet ray absorber is dissolved in an aramid dope solution, and the resultant dope solution is shaped, for example, into filaments, if the shaping temperature is high, the conventional ultraviolet ray absorber is usually decomposed and thus the resultant shaped article does not exhibit satisfactory light resistance.
Also, after shaping, in the resultant PPTA article, it is very difficult to fix an additive within the PPTA polymer due to a barrier derived from a high crystallinity and intermolecular chain force of the PPTA polymer. To enhance the light resistance of the para type aramid, it has been attempted to make an ultraviolet ray absorber to be contained in water-swollen, non-dried aramid fibers, as disclosed in Japanese Unexamined Patent Publication Nos. 49-75,824, 50-12,322, 53-35,020, 56-33,487 and 1-240,533. This attempt is, however, disadvantageous in that the impregnation of the p-aramid fiber with the ultraviolet ray absorber causes the intermolecular structure of the fiber to be disarranged and thus the mechanical properties such as tensile strength of the fiber are adversely affected.
Japanese Unexamined Patent Publication No. 5-9,293 discloses a method of enhancing the light resistance of the aramid by blending an aromatic amide compound having a naphthalene ring structure thereto. Where the compound is an oligomer produced by a polymerization different from that of the aramid, and the oligomer production is carried out at an industrial scale, generally, it is necessary to provide an oligomer producing reaction vessel separate from the aramid polymerization vessel and thus the number of the necessary reaction processes increases. If the aromatic amide compound has a lower molecular weight than that of the oligomer, the lower molecular weight amide compound sometimes sublimates during a heat-drawing or heat treating procedure. Also, most all of the fibers blended with the aromatic amide compound exhibit degraded mechanical properties.
Other attempts have been made to produce shaped articles from a blend of an aramide with an aromatic amide compound having a naphthalene ring stricture. For example, Japanese Unexamined Patent Publication No. 62-263,320 discloses a fiber consisting of a mixture of an aromatic copolyamide made by using a monomer having a naphthalene ring structure with a poly-paraphenylene terephthalamide, and Japanese Unexamined Patent Publication No. 3-143,922, especially Example 8 thereof, discloses an aramid fiber produced from a blend of a dope of an aramid having a naphthalene structure with a dope of another aramid having no naphthalene structure. The purpose of these attempts is to enhance the mechanical strength of the aramide fiber.
Japanese Examined Patent Publication (Kokoku) No. 62-10,580 discloses a method of improving the light resistance of a polyester, polycarbonate or polyamide by mixing a light heat resistant aromatic orthohydroxyamide compound, as an ultraviolet ray absorber, into the polymer. At the present time, it is well known that nylon polymers which are aliphatic polyamides are clearly distinguished from wholly aromatic polyamides, namely aramids. In the examples of the Japanese publication (Kokoku), only nylon 6 is employed as an example of the polyamide, and the Japanese publication is completely silent as to aramids. Also, although this Japanese publication discloses that aramids containing the aromatic orthohydroxyamide compound absorb ultraviolet rays at a specific wavelength or lower, the publication does not teach any mechanical property of the aramids. This is due to the fact that the aromatic orthohydroxyamide compound has a low solubility in the aramide and a poor heat resistance and exhibits an ultraviolet ray-shielding effect too low to prevent the deterioration of the aramide by the light. According, it is further demanded to provide a new ultraviolet ray absorber having an enhanced ultraviolet ray-shielding activity, heat resistance and compatibility with the aramids, and thus capable of enhancing the mechanical properties of the aramids. Further, among the aromatic hydroxyamide compounds disclosed in Japanese Examined Patent Publication No. 62-10,580, the compounds terminated at two ends thereof with naphthol carboxylic acid groups are provided with a middle diamine portion having a toxic benzidine structure, and thus this compound poses the risk of exhibiting toxicity when hydrolyzed.
Dokl Akad., Nauk BSSR, 23 (4), 347 (1979) and J. Appl. Polym. Sci., 23 (8), 2225 (1979) state that orthohydroxy salicylic acid amide compounds effectively enhance the light resistance of polymeric materials such as polyethylene or natural rubber. However, these compounds are unsatisfactory in ultraviolet ray-shielding activity and heat resistance. Also, these publications are completely silent as to the specific ultraviolet ray-absorbing compounds of the present invention and the specific advantages thereof.